Monolithic linear polishing sheet

ABSTRACT

A chemical mechanical polishing article can be a single contiguous layer having a polishing surface, the layer being an elongated substantially rectangular sheet having a width and a length at least four times greater than the width. Forming a polishing article can include depositing a liquid precursor on a moving belt, at least partially curing the liquid precursor while on the moving belt to form a polishing layer, and detaching the polishing layer from the belt.

TECHNICAL FIELD

This disclosure relates to chemical mechanical polishing.

BACKGROUND

An integrated circuit is typically formed on a substrate by thesequential deposition of conductive, semiconductive or insulative layerson a silicon wafer. One fabrication step involves depositing a fillerlayer over a patterned stop layer, and planarizing the filler layeruntil the stop layer is exposed. For example, trenches or holes in aninsulative layer may be filled with a conductive layer. Afterplanarization, the portions of the conductive layer remaining betweenthe raised pattern of the insulative layer form vias, plugs and linesthat provide conductive paths between thin film circuits on thesubstrate. Planarization can also be used to provide a planar surfacefor photolithography.

Chemical mechanical polishing (CMP) is one accepted method ofplanarization. This planarization method typically requires that thesubstrate be mounted on a carrier or polishing head. The carrier headplaces the exposed surface of the substrate against a polishing pad andprovides a controllable load, i.e., pressure, on the substrate. Apolishing liquid, such as an abrasive slurry, is supplied to the surfaceof the polishing pad.

In one type of polishing system, the polishing pad is a linear sheetthat is incrementally advanced across a platen.

SUMMARY

In one aspect, a chemical mechanical polishing article is a singlecontiguous layer having a polishing surface, the layer being anelongated substantially rectangular sheet having a width and a length atleast four times greater than the width.

Implementations may include one or more of the following features. Thelayer may be polyurethane, e.g., a porous polyurethane. The layer mayhave a thickness between about 30 and 50 mils. The polishing surface mayinclude a plurality of grooves extending partially but not entirelythrough the polishing pad. The grooves may have a depth between about 15and 30 mils. At least a portion of the layer may be wound in a roll. Thelayer may have a length between about twenty and thirty feet, and awidth between about two and four feet.

In another aspect, a chemical mechanical polishing article includesfirst and second sheet portions, and a window extending the length ofand connecting the first and second sheet portions. Each sheet portionconsists of a single contiguous layer having a polishing surface, andeach sheet portion is an elongated substantially rectangular sheethaving a width and a length at least four times greater than the width.

In another aspect, a chemical mechanical polishing assembly includes afeed roller, a take-up roller, and a polishing sheet having a first endwound around the feed roller and a second end wound around the take-uproller. The polishing sheet consists of single contiguous layer having apolishing surface, the layer being an elongated substantiallyrectangular sheet having a width and a length at least four timesgreater than the width.

In another aspect, a method of forming a polishing article includesdepositing a liquid precursor on a moving belt, at least partiallycuring the liquid precursor while on the moving belt to form a polishinglayer, and detaching the polishing layer from the belt.

Implementations may include one or more of the following features. Theliquid precursor may be deposited onto a carrier sheet, e.g., apolyethylene terephthalate polyester film, supported on the belt. Thepolishing layer may be removed from the carrier sheet. Top and bottomsurfaces of the polishing layer may be ground. At least partially curingthe liquid precursor may include heating. The polishing sheet may befully cured after the polishing sheet is detached from the belt. Thepolishing sheet may be compressed, e.g., passed between pinch rollers.Grooves may be formed in the polishing sheet. Edges of the polishingsheet may be trimmed.

Advantages may include the following. The polishing layer can be thickerwithout reducing the length of the sheet wrapped around the feed roller,thus increasing pad life. Optical transmission through a window in thepolishing sheet can be improved.

Other features and advantages will be apparent from the followingdescription, including the drawings and claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic exploded perspective view of a chemical mechanicalpolishing (CMP) apparatus.

FIG. 2 is a top plan view of the CMP apparatus of FIG. 1.

FIG. 3A is a top plan view, cut away, of the first polishing station ofthe CMP apparatus of FIG. 1.

FIG. 3B is a schematic exploded perspective view of a rectangular platenand a polishing cartridge.

FIG. 3C is a schematic perspective view of a polishing cartridgeattached to a rectangular platen.

FIG. 4 is a schematic perspective view, cut away of a linear polishingsheet.

FIG. 5A is a schematic side view in cross-section of an implementationof the polishing sheet.

FIG. 5B is a schematic side view in cross-section of anotherimplementation of the polishing sheet.

FIG. 5C is a schematic side view in cross-section of anotherimplementation of the polishing sheet.

FIG. 6 is a schematic side view of a feed roller of the polishingcartridge.

FIG. 7 is a schematic perspective view, cut away, of anotherimplementation of the polishing sheet.

FIG. 8 is a schematic side view of a machine to manufacture thepolishing sheet of FIG. 7.

FIG. 9 is a schematic top view of an implementation of the polishingsheet.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, one or more substrates 10 will be polishedby a chemical mechanical polishing apparatus 20. A description of asimilar polishing apparatus may be found in U.S. Pat. No. 6,244,935, thedescription of which is incorporated by reference. Polishing apparatus20 includes a machine base 22 with a table top 23 that supports a seriesof polishing stations, including a first polishing station 25 a, asecond polishing station 25 b, and a final polishing station 25 c, and atransfer station 27.

Each polishing station includes a rotatable platen. At least one of thepolishing stations, such as first station 25 a, includes a polishingcartridge 102 mounted to a rotatable, rectangular platen 100. Thepolishing cartridge 102 includes a linearly advanceable sheet or belt ofpolishing material. The remaining polishing stations, e.g., secondpolishing station 25 b and final polishing station 25 c, may include“standard” circular polishing pads 32 and 34, respectively, eachadhesively attached to a circular platen 30. Each platen may beconnected to a platen drive motor that rotates the platen.

Each polishing station 25 a, 25 b and 25 c also includes a slurrydelivery port, a pad rinse system (which can be a combined slurry/rinsearm 52 that projects over the associated polishing surface) and a padconditioner apparatus 40.

A rotatable multi-head carousel 60 is supported above the polishingstations by a center post 62 and is rotated about a carousel axis 64 bya carousel motor assembly (not shown). Carousel 60 can include fourcarrier head systems mounted on a carousel support plate 66 at equalangular intervals about carousel axis 64. Three of the carrier headsystems receive and hold substrates, and polish them by pressing themagainst the polishing sheet of station 25 a and the polishing pads ofstations 25 b and 25 c. One of the carrier head systems receives asubstrate from and delivers a substrate to transfer station 27.

Each carrier head system includes a carrier or carrier head 80. Acarrier drive shaft 78 connects a carrier head rotation motor 76 (shownby the removal of one quarter of the carousel cover) to carrier head 80so that each carrier head can independently rotate about its own axis.In addition, each carrier head 80 independently laterally oscillates ina radial slot 72 formed in carousel support plate 66.

Referring to FIGS. 3A, 3B, and 3C, polishing cartridge 102 is detachablysecured to rectangular platen 100 at polishing station 25 a. Polishingcartridge 102 includes a feed roller 130, a take-up roller 132, and agenerally linear sheet 110 (which can be considered to form a polishingbelt or web) of a polishing pad material. The polishing sheet (ifcompletely unwound from the rollers) has a length significantly greaterthan its width. An unused or “fresh” portion 120 of the polishing sheetis wrapped around feed roller 130, and a used portion 122 of thepolishing sheet is wrapped around take-up roller 132. A rectangularexposed portion 124 of the polishing sheet that is used to polishsubstrates extends between the used and unused portions 120, 122 over atop surface 140 of rectangular platen 100.

The rectangular platen 100 can be rotated (as shown by phantom arrow “A”in FIG. 3A) to rotate the exposed portion of the polishing sheet andthereby provide relative motion between the substrate and the polishingsheet during polishing. Between polishing operations, the polishingsheet can be advanced (as shown by phantom arrow “B” in FIG. 3A) toexpose an unused portion of the polishing sheet. When the polishingmaterial advances, polishing sheet 110 unwraps from feed roller 130,moves across the top surface of the rectangular platen, and is taken upby take-up roller 132.

Referring to FIG. 4, polishing sheet 110 includes a polishing layer witha polishing surface 112, and a leader 160 and a trailer 162 that extendpast the polishing layer (thus, polishing surface 112 does not extend tothe ends of the polishing sheet). The leader and trailer can be formedof a material that is more flexible, and optionally less compressible,than the polishing layer. The leader 160 and trailer 162 can be attachedto the feed and take-up rollers 130 and 132 by tape or a pressuresensitive adhesive on the back of the leader. A peelable liner may beplaced over the tape or adhesive and removed prior to attaching thepolishing sheet 110 to the rollers.

The polishing layer can be a porous polyurethane, and the leader andtrailer can be a thin tear-resistant material, e.g., polyethyleneterephthalate. The polishing layer can be opaque, whereas the leader andtrailer can be transparent. The leader 160 and trailer 162 can beprinted or embossed with information, such as a part number, materialtype, lot number, or polishing layer length.

Grooves can be formed in the polishing surface 112 running across thewidth and transverse to the direction of travel of the sheet The groovescan be about half the depth of the polishing layer, e.g., 18-20 milsdeep. The grooves can have a uniform width and pitch, e.g., about onemillimeter wide and spaced apart by about two to three millimeters.Referring to FIG. 9, the grooves 128 can stop short of the edge of thepolishing layer. Such a groove configuration can improve resistance ofthe polishing pad to tearing.

The backing layer 116 can be about five mils thick. The polishing layercan be between about twenty to thirty feet long, e.g., between twentyand twenty five feet long, and can be between twenty and thirty incheswide, e.g., about twenty-eight inches wide. The leader and trailer 160and 162 have same width as the polishing layer, and can be about sixfeet long.

Referring to FIG. 5A, in one implementation, the polishing sheetincludes a backing layer 116 and a polishing layer 114 formed on thebacking layer 116. In this implementation, the backing layer 116 can bea continuous sheet that spans the polishing layer 114. In the transversedirection (perpendicular to the length and direction of travel of thesheet), the wide edges 164 (along the length of the sheet) of thepolishing layer 114 and backing layer 116 can be aligned so that thepolishing layer and backing layer 116 have the same width. In contrast,in the longitudinal direction (parallel to the length and direction oftravel of the sheet), the backing layer 116 extends past the narrowedges 166 (edges across the width of the sheet) of the polishing layer114 to provide the leader 160 and trailer 162. In the region of theleader 160 and trailer 162, the top surface of the backing layer 116 canbe the outermost surface, i.e., there are no other layers on top of thebacking layer 116. As noted above, the leader 160 and trailer 162 can beprinted or embossed with information, such as a part number, materialtype, lot number, or polishing layer length.

The polishing layer 114 can be a porous polyurethane, and the backinglayer 116 can be a thin, flexible, generally incompressible,fluid-impermeable sheet, e.g., polyethylene terephthalate. The backinglayer 116 can be transparent. The polyurethane layer an be 35-40 milsthick. The polishing layer 114 can be laid down as a single continuousunbroken layer. Alternatively, the polishing layer 114 can be tiled inadjacent strips, e.g., two to four feet long.

The polishing layer 114 can be secured to the top surface of the backinglayer 116 by an adhesive 170, e.g., a pressure-sensitive adhesive layer.For example, the polishing layer 114 and backing layer 116 can befabricated separately and then adhered together. Alternatively, thepolishing layer 114 can adhere to the backing layer 116 backing layerwithout an adhesive. For example, a liquid polishing layer precursor canbe dispensed onto the backing layer 116 and cured so as to form apolishing layer 114 adhering to the backing layer 116.

Referring to FIG. 5B, in another implementation, the polishing sheetincludes a backing layer 116 and a polishing layer 114 formed on thebacking layer 116, but the leader 160 and trailer 162 are separatepieces 172 bonded to the backing layer 116. In this implementation, thebacking layer 116 can be a continuous sheet that spans and hascoextensive edges with the polishing layer 114.

The polishing layer 114 can be a porous polyurethane. The backing layer116 can be either softer or less compressible than the polishing layerand can be transparent or opaque. For example, the backing layer can bea soft subpad such as a urethane-impregnated fibrous mat, or a generallyincompressible layer such as polyethylene terephthalate. The separatepieces 172 can be thin, flexible, tear-resistant, generallyincompressible, fluid-impermeable sheets, e.g., polyethyleneterephthalate.

As discussed above, the polishing layer 114 can be secured to thebacking layer with or without an adhesive. The leader and trailer pieces172 can be secured to the backing layer 116 with a butt joint and a thintape 174 on the underside of the polishing sheet.

Referring to FIG. 5C, in another implementation, the polishing sheetincludes a polishing layer 114 without any backing layer, and the leader160 and trailer 162 are separate pieces bonded to the polishing layer114. The polishing layer 114 can be a porous polyurethane. The tensilestrength of the polishing layer 114 can be about 22 MPa (>3000 psi),which should exceed the average stresses applied while vacuum chuckingthe web onto the platen (˜14 psi) or while advancing the web (˜100 psi).

The separate pieces 172 can be thin, flexible, tear-resistant, generallyincompressible, fluid-impermeable sheets, e.g., polyethyleneterephthalate. The leader and trailer pieces 172 can be bonded to thepolishing layer 114 by a thin tape 174 on the underside of the polishingsheet.

In each of the above implementations, since the polishing layer does notextend to the edges of the polishing sheet, the polishing sheet can befabricated using less polishing layer material, and thus at lower costin comparison to a polishing sheet having the polishing layer across theentire length.

Referring to FIGS. 3B and 6, feed and take-up rollers 130 and 132 shouldbe slightly longer than the width of polishing sheet 110. The rollers130, 132 may be plastic or metal cylinders slightly longer than thewidth of the polishing sheet and about 2″ in diameter. The opposing endfaces 134 of feed roller 130 (only the feed roller is shown in FIG. 6,but the take-up roller would be constructed similarly) can each includea recess 136 which will engage support and drive mechanisms on theplaten. For example, one end face can include keyed slot into which analignment pin will fit, and the other end face can include a keyed starpattern into which a drive gear will fit. In addition, both ends of eachroller can include a circular flange 138 that projects above the surfaceof the roller to hold the polishing sheet in place and prevents it fromsliding off either side of the roller.

Because the leader and trailer can be more flexible than the polishinglayer, they can be easier to manipulate and thus easier to install onthe rollers. In addition, because the leader and trailer can be moreflexible than the polishing layer, the leader and trailer can be woundmore tightly on the roller. This permits the diameter of the roller tobe decreased, thus either reducing the volume required by the cartridgeor permitting more polishing material to be stored in the cartridge.

Referring to FIG. 7, in another implementation, the polishing sheet is asingle layer, specifically a polishing layer 114 with a polishingsurface 112 but without any backing layer or carrier film, and without aleader or trailer. The polishing layer 114 is a contiguous andmonolithic layer; the entire length of the polishing layer between thefeed and take-up roller is an uninterrupted seamless part, e.g., thereis no adhesive connection between separate pieces, and the entirepolishing layer 114 is generally of uniform composition. In someimplementations, the polishing layer is formed without heat-basedmolding of separate pieces (such molding should generate regions ofslightly different consistency where the molding occurs, and thepolishing layer 114 can be sufficiently homogeneous to lack suchregions). The polishing layer 114 has sufficient cohesive strength andmechanical integrity to avoid tearing under the mechanical forcesapplied in typical CMP process conditions. The polishing layer 114 canbe a porous polyurethane. The length of the polishing layer 114 can beat least six times greater than the width. For example, the polishinglayer 114 can be about two to three feet wide, e.g., 2.5 feet wide, andthirty to forty feet long. Although illustrated in FIG. 7 in a flatstate, in use the end portions of the polishing sheet 114 would be woundin a roll around take-up and feed rollers, e.g., as shown in FIG. 3B. Aration of length to width of the polishing sheet can be at least 4:1,e.g., 12:1.

The polishing layer 114 can be about 30 to 50 mils thick. Because thebacking layer and adhesive that would hold the backing layer to thepolishing layer are eliminated, the polishing layer can be made thickerand yet the same length of polishing sheet can be wound around a spindlewithout increasing the diameter of the polishing magazine. Since thepolishing layer 114 is thicker, the number of substrates polished perunit length of the polishing sheet can increase, and thus the pad lifecan increase. For example, in comparison to a polishing sheet with a 40mil thick polishing layer, a 5 mil thick backing layer and a 5 mil thickadhesive, a polishing sheet 50 mil thick polishing layer (but no backinglayer or adhesive) should have about a 20-33% increase in capacity.Grooves extending partially but not entirely through the polishing layerpad, e.g., having a depth between about 15 and 30 mils, e.g., about halfthe thickness of the polishing layer, can be formed in the polishingsurface 112 of the polishing layer 114.

Where a window stripe is formed in the polishing sheet, the two portionson either side of the stripe can each be a single contiguous layer. Thesides of the window can be molded to the sides of the polishing layerportions.

Referring to FIG. 8, a method of producing such a monolithic polishingsheet is to deposit a liquid precursor 200 onto a moving belt 210. Thelayer of liquid precursor on the belt 210 can be subjected to a firstcuring process, e.g., the belt and layer can pass through an oven 212 orother heat source, to at least partially cure the precursor into asemi-solid sheet 202. The semi-solid sheet 202 can then be detached frombelt and pass between pinch-rollers 214, 216 that compress the sheet toa desired thickness. In addition, protrusions on one of the pinchrollers 216 can imprint grooves into the surface of the semi-solid sheet202. Then the sheet 202 can be subjected to a second curing process,e.g., additional heat, such as from the second over 220 to be cured to afinal desired rigidity. Edges of the sheet 202 can be trimmed to providea polishing sheet of uniform width, and if necessary the polishing sheetcan be smoothed and/or thinned, e.g., with a grinder or by passingbetween blades that will skive off top and bottom portions of the sheet,to remove burrs or other defects. A similar process can be used toproduce the polishing layer 114 for the implementation of FIG. 5C.

In some implementations, a polishing sheet can be formed by casting thepolyurethane precursor material on a carrier sheet (e.g., with thecarrier sheet on the moving belt or supported on spaced-apart rollers sothat the carrier sheet provides a moving belt-like surface), andsubjecting the precursor to the first curing step. The carrier sheet canpeeled off either before or after the final cure step. Both sides of thepolish sheet can then be skived, ground and/or sanded to adjust padthickness and remove any cured crust layer.

Grooves can be formed on the cured polishing sheet using a cutting toolsuch as a knife blade. If the grooves are formed by imprinting withpatterned rollers and a subsequent cure step, by selecting anappropriate degree of compression, the grooves could be formed with asmooth or non-porous surface layer in the grooves (in contrast, thepolishing surface itself can be porous, and grooves formed in a porouspad with a knife have porous walls and bottoms). If so, waste productsor polishing debris can be less likely to remain trapped in the grooves,thus reducing the potential for defects, e.g., scratches.

Returning to FIGS. 3A, 3B and 3C, rectangular platen 100 includes agenerally planar rectangular top surface 140 bounded by a feed edge 142,a take-up edge 144, and two parallel lateral edges 146. A groove 150(shown in phantom in FIGS. 3A and 3C) is formed in top surface 140. Thegroove 150 can be a generally-rectangular pattern that extends alongedges 142, 144, 146 of top surface 140. Alternatively, vacuum groove 150can be circular and about 29″ in diameter, and the polish area describedby the motion of the head and platen contained within area described bythe dashed lines 150 in FIG. 3A.

A passage through platen 100 connects groove 150 to a vacuum source.When passage is evacuated, exposed portion 124 of polishing sheet 110 isvacuum-chucked to top surface 140 of platen 100. This vacuum-chuckinghelps ensure that lateral forces caused by friction between thesubstrate and the polishing sheet during polishing do not force thepolishing sheet off the platen. Optionally, a central region 148 of topsurface 140 can be free from grooves to prevent potential deflection ofthe polishing sheet into the grooves from interfering with the polishinguniformity.

An unillustrated compressible backing pad can be placed on the topsurface of the platen to cushion the impact of the substrate against thepolishing sheet. In addition, platen 100 may include an unillustratedshim plate. Shim plates of differing thickness may be attached to theplaten to adjust the vertical position of the top surface of the platen.The compressible backing pad can be attached to the shim plate.

In some implementations, the rectangular platen 100 also includes fourretaining flanges 156 that hold feed and take-up rollers 130 and 132 atfeed and take-up edges 142 and 144, respectively. Each retaining flange156 includes a projection or detent that can engage the correspondingfeature on the end of the rollers 130 or 132.

The rollers 130 and 132 can be positioned sufficiently below top surface140 so that the polishing sheet stays in contact with the feed andtake-up edges 142 and 144 of the platen when the entire polishing sheetis wound around either roller. This assists in the creation of a sealbetween the polishing sheet and the rectangular platen when vacuum isapplied to the passage to vacuum-chuck the polishing sheet to theplaten. Furthermore, feed edge 142 and take-up edge 144 of the platenare rounded to prevent abrasion of the underside of the polishing sheetas it moves across the platen.

A transparent strip 118 can be formed along the length of polishingsheet 110. The transparent strip may be positioned at the center of thesheet, and may be about 0.6 inches wide. With respect to FIGS. 5A and5B, transparent strip 118 may be formed by removing the upper layer 114from this region of the transparent backing layer 116. With respect toFIG. 5C, a transparent strip 118 may be formed by molding a window intothe polishing layer 114. The transparent strip 118 can be aligned withan aperture or transparent window 154 in rectangular platen 100 toprovide optical monitoring of the substrate surface for end pointdetection.

Referring again to FIGS. 3A, 3B and 3C, in operation, exposed portion124 of polishing sheet 110 is vacuum-chucked to rectangular platen 100by applying a vacuum to the passage. A substrate is lowered into contactwith polishing sheet 110 by carrier head 80, and both platen 100 andcarrier head 80 rotate to polish the exposed surface of the substrate.After polishing, the substrate is lifted off the polishing pad by thecarrier head. The vacuum on passage 152 is removed. The polishing sheetis advanced to expose a fresh segment of the polishing sheet. Thepolishing sheet is then vacuum-chucked to the rectangular platen, and anew substrate is lowered into contact with the polishing sheet. Thus,between each polishing operation, the polishing sheet may be advancedincrementally. If the polishing station includes a cleaning apparatusthe polishing sheet may be washed between each polishing operation.

The amount that the sheet may be advanced will depend on the desiredpolishing uniformity and the properties of the polishing sheet, butshould be on the order of 0.05 to 1.0 inches, e.g., 0.4 inch, perpolishing operation. Assuming that the exposed portion 124 of polishingsheet is 20 inches long and the polishing sheet advances 0.4 inchesafter each polishing operation, the entire exposed portion of thepolishing sheet will be replaced after about fifty polishing operations.

In another embodiment, a polishing sheet can be fabricated with apolishing layer disposed on a carrier layer, e.g., a polyethyleneterephthalate polyester film, e.g. a Mylar sheet. In someimplementations, the polishing sheet can be formed by casting thepolyurethane precursor material on a carrier layer as discussed above(e.g., with the carrier layer on the moving belt). However, rather thanremoving the carrier layer, the polishing layer remains on the carrierlayer to form the final polishing sheet. In this case, grinding andsurface finishing operations to adjust the polishing layer thickness orroughness would take place only on the top surface. In someimplementations, the initial carrier layer is removed, grinding andsurface finishing operations are performed, and the polishing layer canthen be attached to a new carrier layer for the final polishing sheet

The invention is not limited to the embodiment depicted and described.Rather, the scope of the invention is defined by the appended claims.

1. A chemical mechanical polishing article, consisting of: a singlecontiguous layer having a polishing surface, the layer being anelongated substantially rectangular sheet having a width and a length atleast four times greater than the width.
 2. The article of claim 1,wherein the layer comprises polyurethane.
 3. The article of claim 2,wherein the layer comprises a porous polyurethane.
 4. The article ofclaim 1, wherein the layer has a thickness between about 30 and 50 mils.5. The article of claim 1, wherein the polishing surface includes aplurality of grooves extending partially but not entirely through thepolishing pad.
 6. The article of claim 5, wherein the grooves have adepth between about 15 and 30 mils.
 7. The article of claim 1, whereinat least a portion of the layer is wound in a roll.
 8. The article ofclaim 1, wherein the layer has a length between about twenty and thirtyfeet.
 9. The article of claim 1, wherein the layer has a width betweenabout two and four feet.
 10. A chemical mechanical polishing article,consisting of: first and second sheet portions, each sheet portionconsisting of a single contiguous layer having a polishing surface, eachsheet portion being an elongated substantially rectangular sheet havinga width and a length at least four times greater than the width; and awindow extending the length of and connecting the first and second sheetportions.
 11. A chemical mechanical polishing assembly, comprising: afeed roller; a take-up roller; and a polishing sheet having a first endwound around the feed roller and a second end wound around the take-uproller, the polishing sheet consisting of single contiguous layer havinga polishing surface, the layer being an elongated substantiallyrectangular sheet having a width and a length at least four timesgreater than the width.
 12. A method of forming a polishing article,comprising: depositing a liquid precursor on a moving belt; at leastpartially curing the liquid precursor while on the moving belt to form apolishing layer; and detaching the polishing layer from the belt. 13.The method of claim 12, wherein depositing the liquid precursor includesdepositing the liquid precursor onto a carrier sheet supported on thebelt.
 14. The method of claim 13, wherein the carrier sheet comprises athin polyethylene terephthalate polyester film.
 15. The method of claim13, further comprising removing the polishing layer from the carriersheet.
 16. The method of claim 15, further comprising grinding top andbottom surfaces of the polishing layer.
 17. The method of claim 12,wherein at least partially curing the liquid precursor includes heating.18. The method of claim 12, further comprising fully curing thepolishing sheet after the polishing sheet is detached from the belt. 19.The method of claim 12, further comprising compressing the polishingsheet.
 20. The method of claim 15, wherein compressing includes passingthe polishing sheet between pinch rollers.
 21. The method of claim 12,further comprising forming grooves in the polishing sheet.
 22. Themethod of claim 12, further comprising trimming edges of the polishingsheet.